Latent or persistent reservoirs of HIV infection are thought to give rise to renewed viral replication following cessation of HAART. It is felt that the presence of these reservoirs dictates that patients must remain on antiviral therapy for life. Thus any increased understanding of the biology of latent reservoirs would be quite important. In addition, devising ways to purge latent or persistent reservoirs may hold promise for the treatment of HIV disease. Our laboratory has earlier proposed an activation/elimination approach whereby latently infected cells are activated to express virus, and subsequently targeted for destruction by specific anti-HIV immunotoxins. We now have at our disposal several novel synthetic protein kinase (PKC) activators that appear to be quite active in their ability to induce the expression of latent HIV. We are also exploring novel nanoparticle delivery vehicles, which can specifically target activating agents to CD4-bearing cells. In addition, we have found reproducible latent reservoirs in the thymus, blood and spleens of an improved humanized mouse model, the BLT mouse. We will couple these systems to gain a greater understanding of the biology of latent HIV infection. We will also use these systems to develop a strategy to activate latent HIV, in both in vitro and in vivo systems. We will accomplish this through the following Specific Aims: 1) Define and characterize the various viral reservoirs in the BLT mouse model; 2) Characterize and optimize novel PKC activators coupled with new delivery methods for stimulating viral reservoirs in vitro and ex vivo; 3) Explore the use of novel PKC activators and delivery methods to stimulate latent HIV in BLT mice on HAART. We hope that these studies will provide proof-of-concept that specific activation of viral reservoirs can be accomplished in vivo, and that valuable pre-clinical data regarding this approach will be obtained. If successful, these studies could pave the way for future clinical trials of this type of approach to decrease or eliminate persistent viral reservoirs.